The invention relates to a two-for-one twisting spindle.
The two-for-one twisting spindle described in British Patent Specification No. 1497756 has a compressed-air-actuated threading device by means of which the yarn is drawn in to the hollow axle of the spindle by injector action and is coveyed through a yarn guide passage of a yarn reserve disc by the jet of compressed air. In this compressed-air-actuated threading device, an injector nozzle is disposed directly above the spindle rotor and is directed towards the yarn reserve disc, and a passage forming part of a basket or protection pot leads from the outer periphery thereof to the injector nozzle, a source of compressed air being connectible to the external mouth of the passage by way of a connection piece.
In another two-for-one twisting spindle of this kind described in, for example, German Patent Specification No. 27 33 318, the compressed air passage extends substantially parallel and adjacent to the yarn entry tube.
It is common knowledge that two-for-one twisting spindles tend to draw in yarns after breakage of the yarn. The undesireable effect on a two-for-one twisting spindle is caused by physical factors, particularly by the ventilating action of the spindle rotor and the centrifugal forces which act in the spindle rotor upon the portion of the yarn remaining therein. After the yarn, which has been drawn in in this manner, emerges from the spindle rotor, the yarn either forms a lap on the neck of the wharve or on the rotor, or the yarn is broken on parts of the machine. This results in increased expenditure on maintenance, and, in extreme cases, can lead to interference with the yarn on adjacent spindles and to an increased consumption of power by the spindle.
In order to avoid this phenomenon, a mechanical yarn-catching or yarn-stopping device is chiefly used in two-for-one twisting spindles but, however, leads to additional operating costs and involves a certain amount of operational unreliability. As described in British Patent Specification No. 1047645, a thread-catching or thread-stopping devce is normally pivotably disposed away from the region of the spindle. It usually has a yarn sensor which rests on the yarn. In the event of breakage of the yarn, the thread-catching or thread-stopping device pivots towards the yarn running from the feed bobbin. Either the device, by means of a special catching head, prevents further yarn from being pulled off the bobbin and fed into the spindle, or, for example, the flying yarn is arrested by the stopping device.
An operationally reliable spindle-braking unit which is deescribed in, for example, British Pat. No. 1339211, and which is also controlled by a yarn-sensing device, can be mentioned as a further device for preventing the drawing-in of a yarn after yarn breakage. In the event of yarn breakage, this yarn-sensing device transmits a control pulse to a mechanical or pneumatic device which either disengages the spindle from the drive belt or the drive belt from the spindle by pivoting or displacement. A spindle-braking device of this kind also involves increased structural and operating costs.
An object of the invention is to provide a two-for-one twisting spindle such that the drawing-in of a yarn after breakage is prevented by simple and reliable means, and the yarn is, as far as possible, still held within the spindle.
The present invention comprises a two-for-one twisting spindle in which a compressed-air-actuated device which is adapted to affect or influence the running through of the yarn is disposed in the region of the hollow axle of the spindle (particularly above the spindle rotor), and has an element which is movable substantially at right angles to the path of the yarn and to which a compressed-air passage, extending through a stationary part of the spindle, leads.
In one embodiment, the compressed-air-actuated device includes a piston or lining, which is movable substantially at right angles to the path of the yarn.
In one preferred embodiment of the invention, the compressed-air-actuated device has a compressed-air cylinder whose axis intersects the hollow axle of the spindle at a right angle thereto and whose outer wall has two openings which are located diametrically opposite on another and which are in alignment with the hollow axle of the spindle, the compressed-air cylinder also having a piston which is displaceable within the compressed-air cylinder and whose rear can be subjected to compressed air. When, in an arrangement of this kind, the piston is subjected to compressed air fed through stationary parts of the spindle as a result of a control pulse originating from a yarn sensor after breakage of the yarn, the piston is advanced within the compressed-air cylinder from a rest position into an operating position and it moves at least temporarily into the region of the openings in the outer wall of the compressed-air cylinder which are in alignment with the hollow axle of the spindle, thus interrupting further feeding of the yarn.
Either the yarn can be retained between the piston and a counter-clamping surface by clamping action, or the piston can be provided with a cutting edge for cutting through the yarn.
A compressed-air-actuated thread cutter has already been described in a general form in German Utility Model (Gebrauchsmuster) No. 80 27 354, although this publication does not contain any reference as to how a thread cutter of this kind can be used efficiently in conjunction with a two-for-one twisting spindle.
When the yarn is clamped, the piston can remain in its advanced position until, for example, the commencement of the maintenance work for repairing the yarn breakage.
When the piston, which is adjusted transversely of the hollow axle of the spindle, cuts through the thread in a manner similar to the punch principle, the yarn is held by the yarn brake towards the feed bobbin, while the yarn released towards the take-up bobbin is drawn out of the rotor through the hollow axle under the action of centrifugal force. The spindle itself does not need to be decelerated in order to render the "yarn-clamping device" or "yarn cutter" effective.
The two-for-one twisting spindle in accordance with the invention may be constructed so that it is reliable and simple in operation, no additional space being required owing to the fact that the yarn clamping device or yarn cutter are integrated within the spindle, so that the partitioning of the machine, i.e. the protection of the twisting spindles from one another in the case of the multi-spindle machine, is not affected. The elements required for equipping or converting for a two-for-one twisting spindle are of simple construction and are simple to install. Moreover, the operation of a spindle of this kind is simplified, since an operator no longe has to pay attention to additional elements, such as a yarn braking device which is othewise customary, and which also necessitate a further working operation.